A team around university professor Hans Pretzsch who holds the chair for Forest Growth and Yield examined wood samples from forest testing areas (spruce, pine, beech and oak) that were set up 150 years ago. By means of modern measurement technology it could be shown that wood has gradually become lighter since observations began: Since 1900 by 8 to 12 %. Over the same period of time, volume growth of trees in Central Europe accelerated by 29 to 100%.
The scientists consider the long-term temperature rise (climate change) and the related growing period prolongation causes for the decreasing wood density. Subsequently, a decline in late wood density and an increase of the early wood share were observed. "Lighter wood is less stable and its fuel value is lower", Pretzsch explains. This is essential for many different applications, from timber construction to energy-related utilization. Less stable tree wood also increases the risk of calamities (windthrow and snow break).
"One of the study results important for practical matters showed that the climate-relevant carbon sequestration of forests is overestimated as long as calculations are based on out-of-date wood density values. Extrapolated onto the forests of Central Europe, the traditional estimate is around 10 million t of carbon too high", Pretzsch emphasizes.
